ceph/src/include/Distribution.h

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15
  16 #ifndef CEPH_DISTRIBUTION_H
  17 #define CEPH_DISTRIBUTION_H
  18
  19 #include <vector>
  20
  21 class Distribution {
  22   std::vector<float> p;
  23   std::vector<int> v;
  24
  25  public:
  26   //Distribution() {
  27   //}
  28
  29   unsigned get_width() {
  30     return p.size();
  31   }
  32
  33   void clear() {
  34     p.clear();
  35     v.clear();
  36   }
  37   void add(int val, float pr) {
  38     p.push_back(pr);
  39     v.push_back(val);
  40   }
  41
  42   void random() {
  43     float sum = 0.0;
  44     for (unsigned i=0; i<p.size(); i++) {
  45       p[i] = (float)(rand() % 10000);
  46       sum += p[i];
  47     }
  48     for (unsigned i=0; i<p.size(); i++)
  49       p[i] /= sum;
  50   }
  51
  52   int sample() {
  53     float s = (float)(rand() % 10000) / 10000.0;
  54     for (unsigned i=0; i<p.size(); i++) {
  55       if (s < p[i]) return v[i];
  56       s -= p[i];
  57     }
  58     ceph_abort();
  59     return v[p.size() - 1];  // hmm.  :/
  60   }
  61
  62   float normalize() {
  63     float s = 0.0;
  64     for (unsigned i=0; i<p.size(); i++)
  65       s += p[i];
  66     for (unsigned i=0; i<p.size(); i++)
  67       p[i] /= s;
  68     return s;
  69   }
  70
  71 };
  72
  73 #endif